1. Field of the Invention
The present invention relates to a communications system, a communications device and a communications method in mobile communications systems.
2. Description of the Related Art
In recent years, there have been requests for the implementation of high-speed data communications for use in mobile multimedia services and for the implementation of communications systems which allow a user to use the same mobile terminal in different countries. At these requests, the standardization of next-generation mobile communications systems and the standardization of mobile communications systems using IMT-2000 (third-generation mobile communications systems) have been conducted. The development of these mobile communications systems has been begun. In the standardization of IMT-2000, for example, 3GPP has been used.
FIG. 1 is a diagram illustrating the configuration of a mobile communications system using 3GPP. The mobile communications system has mobile terminals (not shown), base stations (not shown) for conducting radio communications with the mobile terminals, radio access network controllers(not shown, hereinafter “radio access network controller” is referred to as control station), a local switch device(“local switch device” may be referred to as “local switching device” or “local switch”) 105, a gateway switch device(“gateway switch device” may be referred to as “gateway switching device” or “gateway switch”) 107 connected to the local switch device 105 via a network 106 (hereinafter referred to as a core network), a router 108 connected to a public network 109, and a server 110 connected to the public network 109. Also, the term of “switch device” may be referred to as “switching device” or “switch”.
The router 108 is connected to the gateway switch device 107. The router 108 directly connected to the gateway switch device 107 is hereinafter referred to as a correspondence router 108.
Data (e.g., packet data) transmitted from a mobile terminal to a given server 110 is transmitted via a base station or the like to the given server 110. In a mobile communications system using 3GPP, data transmitted from a mobile terminal to a given server 110 is transmitted via one of a plurality of gateway switch devices 107 and a correspondence router 108 connected to the device 107 to the given server 110.
However, the above mobile communication system does not include a means for allowing the selection of a given one of the plurality of gateway switch devices 107 included in communication paths between a mobile terminal and a given server 110 when the mobile terminal transmits data to the given server 110. Similarly, the mobile communications system does not include a means for allowing the selection of a given correspondence router 108 from among a plurality of correspondence routers 108 included in the communication paths between a mobile terminal and a given server 110 when the mobile terminal transmits data to the given server 110.
There has thus been a problem as described below when a mobile terminal transmits data to a given server 110. Data transmitted to a gateway switch device 107 cannot be transmitted by the gateway switch device 107 to a correspondence router 108 in cases as described below. For example, when the CPU of the gateway switch device 107 performs a large amount of processing, or when the capacity of a memory in the gateway switch device 107 is not sufficient, or when the gateway switch device 107 has some trouble in data reception and transmission processes (e.g., a failure occurs in the gateway switch device 107), the gateway switch device 107 (hereinafter referred to as a relay-incapable gateway switch device) cannot transmit the data to the correspondence router 108. As a result, the data cannot be transmitted to the given server 110.
As an existing system for solving the above problem, there is mobile communications system compliant with the standard of PDC-P. FIG. 2 is a diagram illustrating the configuration of a mobile communication system compliant with the standard of PDC-P. In FIG. 2, components identical to those in FIG. 1 are affixed identical reference numerals and will not be described. As shown in FIG. 2, a plurality of gateway switch devices 107 are connected to a local switch device 105 via a core network 106.
This mobile communications system includes means for selecting one of a plurality of correspondence routers 108 when data is transmitted from a mobile terminal to a given server 110. When a gateway switch device 107 connected to the selected correspondence router 108 is capable of relay, the data is transmitted via the gateway switch device 107 and the correspondence router 108 connected to the gateway switch device 107 to the given server 110.
A mobile communications system using the 3GPP standard includes a plurality of correspondence routers 108 capable of transmitting data to a given server 110 when data is transmitted from a mobile terminal to the given server 110. However, the mobile communications system using the 3GPP standard is not provided with a memory for storing a correspondence table (see FIG. 5) in which the address information of servers 110 are associated with the address information of gateway switch devices 107, for example.
If the above mobile communications system is provided with a memory for storing the correspondence table, there is a problem as follows. When data is transmitted from a mobile terminal to a given server 110, the data is first transmitted to a local switch device 105. The local switch device 105 then accesses the correspondence table and obtains the address information of a given gateway switch device 107. The local switch device 105 then transmits the data via the given gateway switch device 107 to the server 110.
For the transmission, the mobile communications system does not establish the process of selecting one of a plurality of gateway switch devices 107 (to which data is transmitted from the local switch device 105) connected to the local switch device 105.
The local switch device 105 also cannot find a plurality of correspondence routers 108 connected to a gateway switch device 107. When transmitting data to a gateway switch device 107, the local switch device 105 cannot transmit instruction information below. The instruction information means an instruction to transmit data via a given correspondence router 108.
When a plurality of correspondence routers 108 are connected to a gateway switch device 107, the following is true. The correspondence routers 108 provide different communication paths between a mobile terminal and a given server 110. Data communications using the different communication paths show different communication abilities (data transmission speeds and data loss rates). In order to transmit data from a mobile terminal to a given server 110 via a communication path exhibiting good communication ability, the following process is required. That is, it is necessary for a given device to select a given correspondence router 108 from among the plurality of correspondence routers 108 as a correspondence router included in a communication path between the mobile terminal and the given server 110.
It is thus desirable that the mobile communications system include a means for selecting one of the plurality of correspondence routers 108 when data is transmitted from a mobile terminal to a given server 110.
A mobile communications system compliant with PDC-P includes a plurality of correspondence routers 108 being capable of transmitting data to a given server 110 when data is transmitted from a mobile terminal to the given server 110. In the mobile communications system, a local switch device 105 can select a given correspondence router 108 from among the plurality of correspondence routers 108 when transmitting data to the given server 110. When a gateway switch device 107 connected to the selected correspondence router 108 is capable of relay, the local switch device 105 can transmit data via the given correspondence router 108 to the given server 110 (FIG. 6).
The above-described conventional art, however, has the following problem. FIGS. 3 and 4 are supplementary diagrams for the description of the problem in the conventional art. When the local switch device 105 transmits data to a gateway switch device (gateway switch device incapable of transmitting data to a correspondence router 108) 107, the conventional PDC-P communications system can only change the communication path on the core network 106. Thus the gateway switch device 107 cannot forward the data to another gateway switch device 107 (FIGS. 3 and 4). A gateway switch device 107 capable of transmitting data to a correspondence router 108 is hereinafter referred to as a relay-capable gateway switch device 107.
When the mobile terminal again transmits data to the given server 110, the data is transmitted to the give server 110 if the local switch device 105 can transmit the data to a relay-capable gateway switch device 107.
However, the conventional local switch device 105 does not manage information about relay-incapable gateway switch devices 107. Thus the local switch device 105 can again transmit data to a relay-incapable gateway switch device 107. In this situation, the data cannot be forwarded from the relay-incapable gateway switch device 107 to another gateway switch device 107. As a result, the data transmitted from the mobile terminal cannot be transmitted to the given server 110.
There has thus been demand for the development of a communications system and a communications device (e.g., a local switch device) which allow data to be transmitted from a switching device (e.g., a gateway switch device) other than a relay-incapable switching device to a server 110 even when the data has been transmitted to the relay-incapable switching device (e.g., the gateway switch device).
In the mobile communications system using PDC-P shown in FIG. 6, as described above, the local switch device 105 can perform the following processing. To transmit data to a given server 110, the local switch device 105 selects a given correspondence router 108 from among the correspondence routers 108 connected to the given server 110. The local switch device 105 can transmit data via the given correspondence router 168 to the given server 110.
The selection of the given correspondence router 108 by the local switch device 105 is performed in a manner as described below.
In a correspondence table stored in a memory 125, information identifying the server 110 (e.g., address information) is associated with information identifying the plurality of correspondence routers 108, and order information is associated with the information identifying each correspondence router 108.
Suppose that the local switch device 105 has selected a given correspondence router 108 (e.g., a correspondence router corresponding to address information a) in the most recent past. When the local switch device 105 selects a correspondence router 108 next time, a correspondence router 108 next in order to the above given correspondence router 108 (e.g., a correspondence router corresponding to address information b; see FIG. 6) is selected (round robin manner).
In a round-robin manner, data transmitted from a mobile terminal is not always transmitted to a given server 110 via a communication path having good communication ability. During the transmission of data transmitted from a mobile terminal to a given server, the following problem can occur. For example, the arrival of the data at the give server can be delayed, data loss can occur, congestion can occur on the network, and congestion in a device on the network can occur.
There has thus been a demand for the development of a communications system which allows data transmitted from a mobile terminal to be transmitted via a communication path having good communication ability to a server 110.
It is common that a user of a mobile terminal makes an agreement (such as a contract) with a service provider, for example. In the agreement, it is stipulated that the service provider provides the user with a kind of information. In some cases, the service provider manages a plurality of servers. In these cases, the user must find out the location information (e.g., the URL) of a server which delivers the above kind of information. Specifically, the user must find out the location information of the server delivering the above kind of information based on the location information of the plurality of servers managed by the service provider. Thus the user cannot easily obtain the above kind of information.
A system in which an information delivery request is transmitted to the server when the user simply inputs information identifying the service provider and the information delivery request using the mobile terminal, would be convenient for the user in the following aspect. The user does not need to find out the location information of the server delivering the above kind of information.
Thus the development of a communications system with increased convenience to users has been desired.